In 2005, the European Journal of Cardio-Thoracic Surgery wrote about a pregnant 25-year-old woman who had developed a disorder affecting her clotting agents, which led to the woman coughing up a smaller bronchial-tree cast.

Gavitt Woodard, a clinical fellow in UCSF’s thoracic-surgery department who helped UCSF transplant and pulmonary surgeon Georg Wieselthaler take the photo, says the size of the clot itself may have been what allowed the man to cough it up.

It’s possible that “because it was so large, he was able to generate enough force from an entire right side of his thorax to push this up and out,” she says. Were it broken up into smaller segments, “he might not have been able to generate the force.”